This application incorporates by reference of Taiwan application Serial No. 090117854, filed Jul. 20, 2001.
1. Field of the Invention
The invention relates in general to a multicolor dye set with high light-fastness and water-fastness, and more particularly to a multicolor dye set with high light-fastness and water-fastness suitable for use in ink-jet printing process.
2. Description of the Related Art
Generally, the multicolor inklet dye set consists of magenta ink, cyan ink, yellow ink, and black ink. Most of the multicolor inkjet dye sets are water-based dye sets in the commercial market. Recently, two more colors, light magenta ink and light cyan ink, have been adopted for adding variety to the inkjet ink. Even light yellow ink is added in the inkjet ink later. The composition of four-color, six-color, or sever-color inkjet ink consists of at least one dye or colorant, water, organic solvent, and other additives. However, the printing image formed by the water-base inkjet dye set has poor water-fastness and light-fastness quality. Hence, the colorant inkjet ink with better water-fastness and light-fastness quality has been aggressively developed in the recent years. Although the colorant inkjet ink has better water-fastness and light-fastness qualities, a need remains for adding the appropriate dispersant and binder. Also, the colorant particle with larger particle size than dye is much easier to precipitate and aggregate around the orifice. The printing image quality is consequently decreased due to the clogging of orifice. Accordingly, it is very important for the researchers to improve the water-fastness and light-fastness of the water-base inkjet dye set.
If the inkjet ink only consists of a single dye, it is easy to cause the plugging of the orifice due to the crystallization of the inkjet dye, so that many kinds of humectants are added in the inkjet ink. But, humectant present in the ink also postpones the time required for drying the printing image, and decreases the water-fastness quality of inklet ink. Addition of humectants are well known and are described in, for example, U.S. Pat. No. 4,631,085 (Kawanishi, et al., 1986), U.S. Pat. No. 4,713,113 (Shimada, et al., 1987), and U.S. Pat. No. 4,737,190 (Shimada, et al., 1988). Also, U.S. Pat. No. 5,925,177 (Carreira, et al., 1999) disclosed an ink composition comprising Acid Yellow 23 dye, urea, and water. Urea presented in the ink avoids the crystallization of Acid Yellow 23 dye, so as to solve the problem of plugging of the orifice.
There are a couple of requirements for a preferred ink and the printing image with better printing quality, such as good crusting resistance, good stability, proper viscosity, proper surface tension, high color saturation, little color-to-color bleed, rapid dry time, etc. During printing, the clogging of the orifice is not going to occur. Additionally, the image printed on the plain paper maintained in a high quality (i.e., high clearness and sharpness, etc.) as printed on the coating paper
Color is represented by two appearance systems. One color appearance system, precisely specifies colors and shows the relationships among the colors, such as Ostwald system, Munsell system, and DIN system. For example, Munsell system, established by an American painter named Munsell, defines colors by the three properties of hue, value, and chroma. Munsell established numerical scales with visually uniform steps for each of these attributes. The other appearance system is a color-mixing system, which defines the color according to a mixing of three primary colors. So far, the Commission Internationale de L""Eclairage (CIE) system is the most important color mixing system, and is used in the present invention. In the CIE system, the color gamut is defined by L*, a*, and b*, which represent the lightness, hue, and chroma (or saturation) of a color, respectively. The hue of a color represented by a* ranges from green of xe2x88x92a to red of +a, and the chroma (or saturation) of a color symbolized by b* ranges from blue of xe2x88x92b to yellow of +b.
Simply stated, whether the color gamut of ink is board can be determined by the CIE chromaticity diagram. Refer to FIG. 1, which shows color gamut comparisons of two different dye sets. The coordinate X represents hue and is denoted as a*, while the coordinate Y represents chroma(or saturation) and is denoted as b*. FIG. 1 indicated that color gamut of the first inkjet dye set 101 is broader than that of the second inkjet dye set 102. Consequently, the colors of the first inkjet dye set 101 are more abundant than that of the second inkjet dye set 102. Additionally, the light-fastness of ink can also be determined by the CIE chromaticity diagram. First, measure the optical property of the fresh printed image is measured, and a first chromaticity diagram is obtained. Second a radiation step is performed on the fresh printed image for a certain period of time. The optical property of the fresh printed image is then measured again, and a second chromaticity diagram is obtained. Finally, the first chromaticity diagram is compared to the second chromaticity diagram. Usually, the space covered by the second chromaticity diagram is smaller than the first chromaticity diagram. The space difference represents the light-fastness of the ink. The larger space difference represents the poorer the light-fastness of the ink. Similarly, the water-fastness of ink can also be determined by the CIE chromaticity diagram.
Accordingly, it is an important goal for the manufacturers and researchers to develop ink compositions exhibiting desirable characteristics of broad color gamut, high quality image, high light-fastness, and even high water-fastness.
It is therefore an object of the invention to provide a water-based multicolor dye set with high light-fastness and high water-fastness.
It is another object of the invention to provide improved ink compositions of multicolor dye set suitable for use in ink-jet printing process. The printed image formed by the ink of the invention has an excellent optical property of high light-fastness and high water-fastness. Also, the ink dye set of the invention exhibits a broad color gamut and great printing quality.
Those objects of the invention can be achieved by providing an ink-jet ink of water-based multicolor dye set with high light-fastness and high water-fastness, at least comprising a multicolor dye set, a surfactant, and an aqueous solvent. The multicolor dye set includes a cyan dye set, a magenta dye set, and a yellow dye set. The cyan dye set comprises direct blue 199 dye, acid blue 9 dye, and direct blue 86 dye. The magenta dye set comprises reactive red 180 dye, acid red 52 dye, and reactive red dye. The yellow dye set comprises acid yellow 23 and direct yellow 86 dye.
The surfactant of the invention is 2-pyrrolidone and EHMPD (2-ethyl-2-methylol-1,3-propylene glycol), which both are present in the ink in an amount of about 4.0 wt %, respectively. The ink-jet ink of the invention further comprises organic solvent such as 1,4-butandiol for enhancing the penetration and dispersion of the ink.
The ink-jet ink of the invention further comprises a pH buffer such as potassium hydroxide, a chelating agent such as urea, a humectant such as PEG (polyethylene glycol), a biocide, a preservative and other additives.
Other objects, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.